Scientific Report 2003-2004 - Cleveland Clinic Lerner Research ...

THE QIN LABORATORYPOSTDOCTORAL FELLOWSSujay Subbayya, Ph.D.Olga Vinogradova, Ph.D.Yanwu Yang, Ph.D.TECHNICAL ASSOCIATEAsta Velyviene, B.S.GRADUATE STUDENTSXiangming (Sean) Kong, M.S.Julia Vaynberg, B.S.Algirdas Velyvis, B.S.Xiaoxia (Susan) Wang, M.S.Dr. Qin is a Staff member inthe LRI Department ofMolecular Cardiology.NMR Depiction of Protein Complexes Leadto Design of Pharmaceutical EffectorsThe primary research aim of our laboratoryis to probe and understand the molecularmechanisms of key biological eventsinvolving biomolecular interactions, notablyprotein-protein and protein-nucleic acidinteractions. The major step toward this goal isthe study of three-dimensional structures anddynamics of proteins and protein complexes atatomic resolution. Our laboratory is engaged inthis study by using state-of-the-art nuclearmagnetic resonance spectroscopy(NMR) as a primary tool,combined with other modernbiology techniques. Severalprojects ongoing in thelaboratory include: (a)structural elucidation ofintegrin signaling involved incell adhesion and cell migration;(b) mechanistic investigationof protein kinase R(PKR) involved in interferonand cellular signaling; and (c)molecular mechanism of redox(oxidation/reduction)regulation. The current majorfocus is to explore themolecular basis of integrinsignaling involved in regulatingcell adhesion and cell migration.Integrins are known to be heterodimeric(α/β) cell surface receptors that mediateadhesion of the cells to one another and to theirsurroundings. Such adhesion is crucial for manybiological processes, such as embryogenesis,hemostasis, the immune response and themaintenance of tissue integrity; and its dysfunctionleads to numerous human disorders, such asthrombasthenia and chronic inflammatorydiseases. Therefore, understanding the mechanismof integrin adhesion is of both physiologicaland pathological importance. The integrins’ability to bind their extracellular ligands foradhesion is tightly regulated through a processtermed inside-out signaling, i.e., a cellular signalstimulates a conformational change in thecytoplasmic domain of an integrin, whichpropagates through its transmembrane region tothe extracellular domain, transforming it from alow-affinity to a high-affinity ligand-binding state(integrin activation). On the other hand, ligandoccupancy of the extracellular domain also elicitssignals back to the cytoplasmic face,which activate cascades ofintracellular responses, ultimatelyconnecting to cytoskeleton(outside-in signaling). In thismanner, the inside and outside ofthe cells are physically linked,resulting in a cooperative regulationof cell functions including celladhesion, migration, cell growthand differentiation. Although thecytoplasmic domains of integrinsare small and devoid of enzymaticactivities, they are the center of bidirectionalsignaling machinery andhence crucial for the control of theintegrin function. Our goal in thisstudy is to elucidate the structuralJun Qin, Ph.D.signalingbasis of the integrin bi-directionalas mediated by the cytoplasmicdomains. A working hypothesis is that thecytoplasmic face adopts distinct conformationsthat direct the inside-out and outside-in signalingprocesses. We are pursuing the structure of thea IIbb 3cytoplasmic complex and its interactionswith their target signaling network. We are alsoworking on determining the structure of theintegrin cytoplasmic domain coupled with thetransmembrane domain. These structures willprovide insights at the atomic level into thecomplex mechanism of integrin activation andsignaling.Nanduri, S., Carpick, B.W., Yang, Y., Williams, B.R., and J. Qin (1998) Structure of the double-strandedRNA-binding domain of the protein kinase (PKR) reveals the molecular basis of its dsRNA-mediated activation.EMBO J. 17:5458-5465.Vinogradova, O., Haas, T., Plow, E.F., and J. Qin (2000) A structural basis for integrin activation by thecytoplasmic tail of the α IIbsubunit. Proc. Natl. Acad. Sci. USA 97:1450-1455.Nanduri, S., Rahman, F., Williams, B.R., and J. Qin (2000) A dynamically tuned double-stranded RNAbinding mechanism for the activation of antiviral protein kinase PKR. EMBO J. 19:5567-5574.Velyvis, A., Yang, Y., Wu, C., and J. Qin (2001) Solution structure of the focal adhesion adaptorPINCH LIM1 domain and characterization of its interaction with the integrin-linked kinase ankyrin repeatdomain. J. Biol. Chem. 276:4932-4939.Vinogradova, O., Velyvis, A., Velyviene, A., Hu, B., Haas, T., Plow, E., and J. Qin (2002) A structuralmechanism of integrin α IIbβ 3‘inside-out’ activation as regulated by its cytoplasmic face. Cell 110:587-597.Shi, J., Krishnamoorthy, G., Yang, Y., Hu, L., Chaturvedi, N., Harilal, D., Qin, J., and J. Cui (2002)Mechanism of magnesium activation of calcium-activated potassium channels. Nature 418:876-880.176